This proposal outline the beginning of a study of the development of avian neural crest cells into neurons. The neural crest is an embryonic structure that gives rise to a large number of cell types in the adult including neurons of the sensory, sympathetic, parasympathetic, and enteric ganglia. The long-range goal of this work is an understanding of the molecular basis of the influences that operate during the development of avian neural crest cells into several types of neurons. In this proposal severl aspects of neurotransmitter metabolism are used as quantitative markers of the neuronal differentiation of neural crest cells in a variety of tissue culture environments. Tissue culture is used because it allows one to control the fluid, substrate, and cellular environment of cells. The aspects of neurotransmitter metabolism examined in this proposal are the synthesis and storage of neurotransmitter candidates, activities of neurotransmitter synthetic enzymes, high affinity uptake of neurotransmitter candidates of their precursors, release of neurotransmitter candidates, cellular location of neurotransmitter systems by autoradiographic methods, and the endogenous content of neurotransmitter candidates. The variables examined in this work include the effect of alterations of the nutrient medium and substrate, the effect of co-culture with several cell types found associated with neural crest cells or their derivatives in the embryo, the role of Nerve Growth Factor, and the effect of electrical activity on the development of neural crest cells into neurons.